Continuous process for the production of low molecular weight polyethers with a DMC catalyst

Abstract

Low molecular weight polyoxyalkylene polyether polyols having a hydroxyl content of from about 3.4 to about 12.1% by weight, and OH numbers of from about 112 to about 400 are produced by a continuous process using a DMC catalyst. In the process of the present invention, oxyalkylation conditions are established in a continuous reactor in the presence of a DMC catalyst; alkylene oxide and a low molecular weight starter are continuously introduced into the continuous reactor; a partially oxyalkylated polyether polyol is recovered from the reactor; and the recovered partially oxyalkylated polyether polyol is allowed to further reactor until the unreacted alkylene oxide content of the mixture is reduced to 0.001% or less by weight. The alkoxylation of the present invention must be carried out a pressure sufficiently high to prevent deactivation of the DMC catalyst. Pressures of from 45 to 55 psia are preferred.

What is claimed is: 
     
       1. A continuous process for the production of a polyoxyalkylene polyether polyol having a hydroxyl content of from about 3.4 to about 12.1% by weight comprising:
 (a) establishing oxyalkylation conditions in a continuous oxyalkylation reactor in the presence of a double metal cyanide catalyst; 
 (b) continuously introducing alkylene oxide and a low molecular weight starter into the continuous oxyalkylation reactor, wherein the starter has a number average molecular weight of from 50 to 250; 
 (c) continuously recovering a partially oxyalkylated polyether polyol from the continuous oxyalkylation reactor; 
 
       wherein (i) the oxyalkylation in the continuous oxyalkylation reactor occurs at a pressure of at least 45 psia to prevent deactivation of the DMC catalyst; (ii) the concentration of unreacted alkylene oxide in the contents of the continuous reactor is maintained at a level of from 1 to 3% by weight; and (iii) the hydroxyl content of the reactor contents is maintained at 3.4 to 12.1% by weight; 
       and
 (d) allowing further reaction of the partially oxyalkylated polyether polyol which is recovered from the continuous oxyalkylation reactor to occur until the unreacted alkylene oxide content of the mixture is reduced to 0.001% or less by weight. 
 
     
     
       2. The process of  claim 1 , wherein the resultant polyoxyalkylene polyether polyol has a hydroxyl number of from about 112 to about 400. 
     
     
       3. The process of  claim 1  wherein the build ratio in the continuous oxyalkylation reactor is from 4.6 to 16.2. 
     
     
       4. The process of  claim 1 , wherein the overall build ratio is from 4.6 to 16.2. 
     
     
       5. The process of  claim 1 , wherein the alkylene oxide is propylene oxide or a mixture of propylene oxide and ethylene oxide that contains at least 85% by weight of propylene oxide. 
     
     
       6. The process of  claim 1 , wherein the hydroxyl content of the reactor contents is maintained at 6 to 11.4% by weight. 
     
     
       7. The process of  claim 1 , wherein the unreacted alkylene oxide in the contents of the continuous oxyalkylation reactor is maintained at a level of from 1 to 2% by weight. 
     
     
       8. The process of  claim 1 , wherein the low molecular weight starter comprises glycerine. 
     
     
       9. The process of  claim 1 , wherein the continuous oxyalkylation reactor is a continuously stirred tank reactor and the further reaction of the partially oxyalkylated polyether polyol is performed in a pipe reactor. 
     
     
       10. The process of  claim 1 , wherein the concentration of the double metal cyanide catalyst in the continuous oxyalkylation reactor is from 30 to 120 ppm, based on the weight of the product. 
     
     
       11. The process of  claim 1 , wherein the pressure in the continuous oxyalkylation reactor is at least 48 psia. 
     
     
       12. The process of  claim 1 , wherein the pressure in the continuous oxyalkylation reactor is from 45 to 55 psia. 
     
     
       13. The process of  claim 1 , wherein the double metal cyanide catalyst is a zinc hexacyanocobaltate catalyst complex. 
     
     
       14. The process of  claim 1 , wherein the resultant polyoxyalkylene polyether polyol has a hydroxyl content of from 7 to 10.6% by weight. 
     
     
       15. The process of  claim 1 , wherein the low molecular weight starter comprises glycerine and the overall build ratio is from 5.2 to 7.9. 
     
     
       16. The process of  claim 1 , wherein the partially oxyalkylated polyether polyol which is recovered from the continuous oxyalkylation reactor passes through a pipe reactor that is steam heated to maintain a high temperature of about 145° C. for reaction of the remaining oxide until the unreacted alkylene oxide content of the mixture is reduced to 0.0005% or less by weight. 
     
     
       17. The process of  claim 1 , wherein the further reaction of the partially oxyalkylated polyether polyol occurs isothermally. 
     
     
       18. A continuous process for the production of a polyoxyalkylene polyether polyol having a hydroxyl content of from about 3.4 to about 12.1% by weight comprising:
 (a) establishing oxyalkylation conditions in a continuous oxyalkylation reactor in the presence of a double metal cyanide catalyst; 
 (b) continuously introducing alkylene oxide and a low molecular weight starter into the continuous oxyalkylation reactor, wherein the starter has at least two hydroxyl groups per molecule and an equivalent weight of up to 115; 
 (c) continuously recovering a partially oxyalkylated polyether polyol from the continuous oxyalkylation reactor; 
 
       wherein (i) the oxyalkylation in the continuous oxyalkylation reactor occurs at a pressure of at least 45 psia to prevent deactivation of the DMC catalyst; (ii) the concentration of unreacted alkylene oxide in the contents of the continuous reactor is maintained at a level of from 1 to 3% by weight; and (iii) the hydroxyl content of the reactor contents is maintained at 3.4 to 12.1% by weight; 
       and
 (d) allowing further reaction of the partially oxyalkylated polyether polyol which is recovered from the continuous oxyalkylation reactor to occur until the unreacted alkylene oxide content of the mixture is reduced to 0.001% or less by weight 
 
       wherein the build ratio in the continuous oxyalkylation reactor is from 4.6 to 16.2 and the overall build ratio is from 4.6 to 16.2, and wherein the temperature of the reaction mixture in further reaction step (d) increases by up to 35° C. as a result of the exothermic polymerization reaction. 
     
     
       19. A continuous process for the production of a polyether polyol having a hydroxyl content of from about 3.4 to about 12.1% by weight, comprising:
 (a) continuously polymerizing at least one alkylene oxide in the presence of a double metal cyanide catalyst in a continuous reactor; 
 (b) feeding a low molecular weight starter that has at least two hydroxyl groups per molecule and an equivalent weight of up to 115, and at least one alkylene oxide to the continuous reactor containing alkylene oxide and a double metal cyanide catalyst;
 recovering a partially oxyalkylated polyol mixture from the continuous reactor 
 
 
       wherein (i) the continuous reactor is maintained at a pressure of from 45 to 55 psia, (ii) the concentration of unreacted alkylene oxide in the contents of the continuous reactor is maintained at a level of from 1 to 3% by weight, and (iii) the hydroxyl content of the reactor contents is maintained at 3.4 to 12.1% by weight; 
       and
 (d) subsequently, the partially oxyalkylated polyol mixture which is withdrawn from the continuous reactor is permitted to further react until the unreacted alkylene oxide content of the mixture is reduced to 0.001% or less by weight 
 
       wherein the build ratio in the continuous oxyalkylation reactor is from 4.6 to 16.2 and the overall build ratio is from 4.6 to 16.2, and wherein the temperature of the reaction mixture in the further reaction step increases by up to 35° C. as a result of the exothermic polymerization reaction. 
     
     
       20. The process of  claim 19 , wherein the resultant polyether polyol has an OH number of from about 112 to about 400. 
     
     
       21. A process for continuously polymerizing an alkylene oxide in the presence of a double metal cyanide polymerization catalyst to form a polyether polyol having a hydroxyl content of from about 3.4 to about 12.1% by weight, wherein:
 (a) in a first step, an initiator compound that has at least two hydroxyl groups per molecule and an equivalent weight of up to 115, and at least one alkylene oxide are fed to a continuous reactor containing a double metal cyanide catalyst, and a partially polymerized mixture is withdrawn from the continuous reactor; 
 
       wherein (i) the continuous reactor is maintained at a pressure of from 45 to 55 psia, (ii) the concentration of unreacted alkylene oxide in the contents of the continuous reactor is maintained at a level of from 1 to 3% by weight, and (iii) the hydroxyl content of the reactor contents is maintained at 3.4 to 12.1% by weight, and
 (b) in a second step, the partially polymerized mixture which is withdrawn from the reactor in step (a) is permitted to further react until the unreacted alkylene oxide content of the mixture is reduced to 0.001% or less by weight 
 
       wherein the build ratio in step (a) is from 4.6 to 16.2 and the overall build ratio is from 4.6 to 16.2, and wherein the temperature of the reaction mixture in step (b) increases by up to 35° C. as a result of the exothermic polymerization reaction. 
     
     
       22. The process of  claim 21 , wherein the resultant polyether polyol has an OH number of from about 112 to about 400. 
     
     
       23. A continuous process for the production of a polyoxyalkylene polyether polyol having an OH number of from 112 to 400 comprising:
 (1) establishing oxyalkylation conditions in a continuous oxyalkylation reactor in the presence of a double metal cyanide catalyst; 
 (2) continuously introducing alkylene oxide and a low molecular weight starter into the reactor, the starter having a number average molecular weight of from 50 to 250; 
 
       and
 (3) continuously recovering a partially oxyalkylated polyether polyol from the continuous oxyalkylation reactor; 
 
       wherein (i) the oxyalkylation is conducted in the continuous reactor at a pressure of at least 45 psia to prevent deactivation of the DMC catalyst; and
 (4) further reacting the partially oxyalkylated polyether polyol which is recovered from the continuous oxyalkylation reactor thereby forming the polyoxyalkylene polyether polyol having an OH number of from 112 to 400. 
 
     
     
       24. The process of  claim 23 , wherein the build ratio in the continuous oxyalkylation reactor is from 4.6 to 16.2 and the overall build ratio is from 4.6 to 16.2, and wherein the reaction temperature of the partially oxyalkylated polyether polyol in step (4) increases by up to 35° C. as a result of the exothermic polymerization reaction. 
     
     
       25. The process of  claim 23 , wherein the oxyalkylation in the continuous reactor occurs at a temperature of at least 135° C. 
     
     
       26. The process of  claim 23 , wherein the partially oxyalkylated polyether polyol which is recovered from the continuous oxyalkylation reactor is reacted isothermally. 
     
     
       27. The process of  claim 23 , wherein the partially oxyalkylated polyether polyol which is recovered from the continuous oxyalkylation reactor is reacted until the unreacted alkylene oxide content of the mixture is reduced to 0.001% or less by weight. 
     
     
       28. A process for continuously polymerizing an alkylene oxide in the presence of a double metal cyanide (DMC) polymerization catalyst to form a polyether polyol having a hydroxyl content of from about 3.4 to about 9.1% by weight, wherein
 (a) in a first step, an initiator compound that has at least two hydroxyl groups per molecule and an equivalent weight of up to 115 and at least one alkylene oxide are fed to a continuous reactor containing a double metal cyanide catalyst, and a partially polymerized mixture is withdrawn from the continuous reactor 
 
       wherein (i) the continuous reactor is maintained at a pressure of from 45 to 55 psia, (ii) the concentration of unreacted alkylene oxide in the contents of the continuous reactor is maintained at a level of from 1 to 3% by weight, and (iii) the hydroxyl content of the reactor contents is maintained at 3.4 to 9.1% by weight, and
 (b) in a subsequent step, the partially polymerized mixture which is withdrawn from the reactor in step (a) is permitted to further react until the unreacted alkylene oxide content of the mixture is reduced to 0.001% or less by weight 
 
       wherein the build ratio in step (a) is from 6.1 to 16.2 and the overall build ratio of from 6.1 to 16.2, and wherein the temperature of the reaction mixture in step (b) increases by up to about 24° C. as a result of the exothermic polymerization reaction.